Ultrasonic cleaning apparatus



3 Sheets-Sheet 1 S. E. JACKE ET AL FIG':1

ULTRASONC CLEAN ING APPARATUS Aug. 30, 1960 Filed March 26, 1958 Aug.30, 1960 s. E. JACKE ETAL ULTRASONIC CLEANING APPARATUS 3 Sheets-Shea?,2

Filed March 26, 1958 INVENTORS. /Wsw/we.

AT ORNEYS.

Aug, 30, 1960 s. E. .JACKE x-:TAL

uLTRAsoNIc CLEANING APPARATUS 3 Sheets-Sheet 3 Filed March 26, 1958 L@/r mW/IJ ifa/m kiwi By ma@ ATTORNEYS.

United States Patent Oliice 2,950,725 Patented Aug. 30, 1960 ULTRASONICCLEANiN G APPARATUS Stanley Emil Jacke, Milford, Lowell C. Newsome,Inkster,

and John W. Collison, Bloomeld Hills, Mich., assignors to DetrexChemical industries, Inc., Detroit, Mlch., a corporation of MichiganFiled Mar. 26, 1958, Ser. No. 724,138

Claims. (Cl. 134-184) This invention relates to improvements inultrasonic cleaning apparatus, and more particularly concerns suchapparatus which includes a piezoelectric transducer contained within ahermetically sealed housing which is submerged in a cleaning liquid. Ithas long been desired to submerge piezoelectric transducers in acleaning liquid and -to protect the piezoelectric ultrasonictransducers, and the cleaning apparatus of which they form a part, fromelectrical disturbances caused by submerging the tranducers in acleaning liquid that is electrically conductive. It has also beendesired to protect the transducers and cleaning apparatus fromcontamination, and 'orn physical and chemical attack by cleaningliquids. Electrically non-conductive cleaning liquids, such astrichlorethylene, may not cause electrical disturbances but mayotherwise attack the transducers.

Heretofore to provide this protection it has been suggested to enclosethe piezoelectric transducers in a housing which has an emittingmembrane with a thickness that is very small, a few percent of the wavelength of the ultrasonic waves emitted. A membrane of this thickness hasa negligible etect on the acoustic coupling between the transducer andthe cleaning liquid. At 400 kilocycles the thickness of such a membraneis .005 inch or less.

However, problems arise in the sealing of this thin membrane to theremainder of the housing containing the transducers. This sealing isdcult to accomplish and the housing is therefore prone to leaks whichpermit the cleaning fluid to enter the housing to attack thetransducers. Another disadvantage of the thin membrane is that it doesnot aiord much protection to the transducers if an object shouldaccidentally be dropped onto it.

It is accordingly an object of this invention to overcome thehereinbefore mentioned disadvantages, and to provide ultrasonic cleaningapparatus which has increased protection, increased eiciency, andincreased intensity of the ultrasonic waves. lt is another object ofthis invention to provide ultrasonic cleaning apparatus which includesan emitting platewhich is strongly constructed to aiord protection tothe transducers. It is another object to substantially reduce thefrequency and impedance matching problems in such apparatus. It isanother object to reduce the frequency drift caused by change in tanktemperature, and thereby substantially reduce adjustment to theelectrical generator when the tank temperature varies. It is anotheryobject of the invention to protect the transducers or electricalconnections from being shorted out by the soils in the cleaning uid; Itis another object of the invention to prevent electrical arcs andshorts. It is another object to eliminate the use of liquid seals andtheir associated gaskets, clamps, or bolts. It is another object toeliminate rubbing contacts between the electrical leads and thetransducers. It is another object to provide a transducer assembly whichis a separate entity, which is not necessarily attached to the wellcontaining the cleaning uid, and which therefore can be submerged at anydesired angle in any shape or size tank large enough to contain it.

Other objects and advantages of this invention will further becomeapparent hereinafter and in the drawings, in which:

Fig. l is a view in elevation of ultrasonic cleaning apparatusconstructed in accordance with this invention with parts being brokenaway in order to illustrate important details;

Fig. 2 is a view in elevation and with parts broken away taken asindicated by the lines and arrows II--II which appear in Fig. 1;

Fig. 3 is a view in top plan of the apparatus shown in Fig. 2;

'Fig 4 is a view on an enlarged scale and partly in section of 'one ofthe ultrasonic -transducer elements;

Fig. 5 is a view of the cleaning liquid and a portion of the ultrasoniccleaning apparatus of Fig. 1, `and shows the apparatus operating andgenerating beams of ultrasonic waves which are focused at a focal zone;

Fig. 6 is a view similar to Fig. 5 and illustrates the operation of twoultrasonic generating units; and

Fig. 7 is a diagrammatic View of the electrical circuit of thetransducers.

In describing the preferred embodiment of the invention illustrated inthe drawings, specific terminology will be resorted to for the sake ofclarity. However, it is not intended to be limited to the specilic termsso selected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish `a similar purpose.

Turning now to the specific embodiments of the invention selected forillustration in the drawings, the number 11 designates generally anultrasonic cleaning apparatus including a well or tank 12 containing acleaning liquid 13 such `as trichlorethylene, and a hermetically sealedhousing 14 which has a focused emitting plate 15 and a plurality of4transducers 16 connected in an electrical circuit with a high frequencyelectrical generator (not shown). Positioned above the level of thecleaning liquid 13 is a conveyor 17 from which is suspended a basket 18which contains a work object 21 submerged in cleaning liquid 13 to becleaned or degreased.

Housing 14 is provided with a bottom plate 22, side walls 23 and 24, andend walls 25, 26. These elements welded together so that housing 14 ishermetically sealed. An aluminum half-coupling 27 is welded in end wall26 and through this coupling pass the electrical wires or coaxial cablewhich extend from the 400 kilocycle electrical generator ,to supplytransducers 16 with power. These electrical wires or cable are encasedwithin an outer conduit which is sealed to coupling 27.

Aluminum ground brackets 28 are welded to the interior l 'fof end walls25, 26 and the brackets 28 support ground connectors 31.

Focused emitting plate 15 is constructed of aluminum and in 400kilocycle apparatus is 0.325 inch, plus or minus 0.002 inch, thick.Plate 15 is formed into iive segments 32, 33, 34, 35, and 36 with anangle of 221/2 degrees between the planes of each adjoining segment.understood that the invention is not limited to five segments or anangle of 221/2 degrees.

As shown in Fig. 4, transducers 16 include barium titanate discs 41which have an upper silver electrode 42 and a lower silver electrode 43.These discs are attached to the underside of focused emitting plate 15by a layer of glue 44 which may be epoxy resin. Transducers 16 form rowsalong the underside of segments 32-36. The lower silver electrodes 43 ofall transducers 16 are electrically connected to the electricalgenerator and the upper silver electrodes 42 are all connected toground.

It is to bed [intense ultrasonic energy.

Any desired electrical circuit may be used to effect these connectionsand one such circuit is shown in Fig. 7. ln Fig. 7 the electricalconnectors are soldered' directly to electrodesAZ, t3-before thetransducers 16 are. potted in the glue layers V44 and attached to lthevunderside of Seg-v ments 3`2-,36. .Y

. YReferring to Fig. 5, thereis shown a focused emitting since suchsoils do not penetrate the hermetically sealed housing 14. Electricalarcs and shorts are prevented and the welded construction eliminates theuse of liquid seals and their associated gaskets, lclamps or bolts. Theelectrical leads are soldered directly to the transducer electrodes,which eliminates the rubbing contacts between and which have beenheretofore proposed. The ultravplate 15a which is formed by segments32m-36a- At.

tachedto the underside of the 'segments are/transducers 16a-16e. ,Thesetransducers, which form rows along Y the segments, generate ultrasonicwaves which are emitted ing liquid is indicated by numeral 54 and theworkobjrect Y kto be .cleaned Vis, indicated by the numeral .55.

Referring to Fig. V6, there is shown the emitting platesY i 15b andicfo'f two` transducer housings andthese'emitting plates are formedl ofsegmentsrS-di and 625-767 which have attached to thelr undersurfaceV thetransducers Y713-74 Varid/'S 179'., YThese transducers generateultrasonicrwaves which form beamsrd-SS and Sii-'93 of ultrasonicwaves'which converge on a focal zone 94.Y The polygonal focal zonesgenerated by plates V15b and 15C may be positioned so they overlap ornot, as desired. The surface ofthe 'beam liquid is indicated by the11umeral 95 and the work object to be cleaned isindicated bythe numeral96.

Incineration, the work object is submerged' in cleaning liquid YT13, theelectrical generator is turned on, andthe transducers. i generateultrasonic waves which 'are emitted through the focused emitting platesrin the form of beams. `which converge on the focalV Zdne Yof YThe work`object is passed through this focal zonewhere it is thoroughlyV cleanedand degreased. v Y Y it is to be noted that the focusingl of theultrasonic beams is of considerable advantage and that it provides forstriking the work object with ultrasonic waves from various angles. Workobjects may be passed below the Vfocal zone as wellas atrthe focalzoneror above it.

With Work objects having large recesses or cavities,v there is adistinctYadvantage 1n passing the work objectA through cleaning liquid in VsuchVa manner that the recess or cavityv passes through the focal zione ofultra-Y Y sonic energywhere this intensified energy can do the mos-t iSince the transducers are contained within a hermetically sealed housing14, such electrical disturbances cannot sonic waveV emitting-apparatuscomprises a separate package contained l,within housing 14, and it iseasily inserted into any tank and positioned therein so as to emit itsultrasonic energy at any desired angle. Y

It is to be understood that theform ofthe invention herein shown anddescribed is to be taken as a preferred embodiment. Various-"changes mayVbe made in the shape, size, andarrangement of parts. Equivalentelements may be substituted for those described herein, parts may bereversed, and certain features of the invention may beutilizedindependentlyl of the use of other features, all'withou't departing fromthe spirit of the invention or the scope of the subio-ined claims. i

Having thus described our inventionywe claim:V Y

1. Ultrasonic cleaningapparatus for cleaning a work object in a wellcontaining a cleaning liquid, said apparatus comprising a hermeticallysealed housing submerged in said liquid; a focused emitting plate foremitting'ultrasonic waves, said emitting plate forming part of saidhousing and being spaced away from said work object, said Yemittingplate being formed of dat segments with the exterior surface of theemitting plate being of generally concave conformation; and a pluralityof flat Vtransducers attached to the'interior'surface of each of saidsegments with the interior surface of the emitting plate being ofgenerally convex conformation, s'aidftransducers and said plateoperating to emit a plurality of beams of ultrasonic waves, Veach ofsaid beams being normal to the surface of the dat segment to which it isat- V-tached, whereby the VVbeams of ultrasonic Waves are focusedandconverge at a focal zone outside of the housins- Y Y V2. The ultrasoniccleaning apparatus defined in claim Y1, wherein said hermeticallysealedhousing is of welded aluminum construction. Y Y

3. Ultrasonic cleaning apparatus forcleanugV ka work i object yin a wellcontaining a cleaning liquid, said apparatus comprising aY hermetically.sealed housing submerged in said liquid; a focused emitting plate foremitting ultrasonic waves of desired wave length, said emitting plateformingpart Yo f saidA housing andY being spaced away plate VbeingyofYgenerally concave conformation, Ysaid is emitting plate being oneV halfof said wave length in thickness;.a plurality of flat transducersattached to the intcrior surface of'each of saidsegments withthe'interiorV surface of the'emitting plate being of generallyl convexYconformation; and a high frequency electrical generator connected incircuit with saidVY transducers; said'transaffect them.'Furthen'hermetically sealed housing 14 pr'o- Y tectsrthe transducersfrom contamination and fromrphysical and chemical attack`V by thecleaning liquids, and the thickness of focused emitting plate 15protects theapparatus fromy damage caused by falling objects.

. 'Another advantage ofthe apparatus is Ythat a high g intensity focused,zoneV ofY ultrasonic Yenergy has been and it reduces the impedancedrift caused by change ofV Ytemperature of the cleaning liquid yin thetankQthereb'y ducers and plate operatingto emita plurality ofV beams ofultrasonic waves, each ofY said beams being normal to the surface 'ofthe flatrsegment to which it isY attached,

whereby the bearns ofl ultrasonic Waves are focused andconverge at afocal one outside of the housing.

4. The Vultrasonic cleaning apparatus deined in claimk 3,Y wherein'psaidtitanate. i 5. Ultrasonic cleaning flat transducers are'hdiscs of bariumobject fin a well containing la 'cleaning liquid, comprissubstantiallyreducing the number of adjustments to the. Y

i electricalV generator ydue to variation in cleaning 'liquid' Ying'ahermeticallyrsealed', Welded aluminum housing submerged in the cleaningliquid; aY focused emitting plate for emitting ultrasonic waves ofdesired Vwave length, saidV emittingplate forming part of said housingand being spaced away from said work-object; saidV emitting plate beingformed of flat-segments with'theexteriorsurface of the emitting platebeing of generally concave Vconformation,.said emitting'plate beingone-half of said apparatus'forcleaning a YworkV Wave length inthickness; a plurality of barium titanate discs glued to the interiorsurface of each of said segments with the interior surface of theemitting plate being of generally convex conformation; and a highfrequency electrical generator connected in circuit With said discs;said discs and plate operating to emit a plurality of beams ofultrasonic waves, each of said beams being normal to the surface of itsat segment, whereby the beams of ultrasonic Waves are focused andconverge at a focal zone outside of the housing.

References Cited in the le of this patent UNITED STATES PATENTS CarlinDec. 11, 1951 Fitzgerald Feb. 12, 1952 Rafuse Mar. 11, 1952 WilliamsMar. 24, 1953 Kearney Apr. 22, 1958 FGREIGN PATENTS Italy Oct. 18, 1956

